1. Field of Invention
This invention relates generally to improvements in designs of gaskets for certain automotive applications. More particularly, the invention relates to improvements in the manufacture of gaskets for a variety of non-combustion sealing gaskets for applications ranging from valve cover, oil pan, and engine water coolant gaskets for thermostats to plenum gaskets for air intake manifolds.
2. Description of the Prior Art
Planar-style gaskets employed in the automotive arena for non-combustion applications including oil pans and valve covers have traditionally been formed of cork materials, wherein the cork materials have often been reinforced with metallic cores to facilitate handling of the gaskets. Such gaskets have been relatively labor-intensive to manufacture, and have not been as effective for sealing as desired, particularly under the rigorous pressure and high temperature demands of modern engines.
In some cases, the cork materials have been bonded to the metallic cores, and adhesive agents employed in the bonding processes have been less than satisfactory, occasionally becoming detached even prior to installation. In other cases, the cork materials have been unable to maintain adequate sealing qualities, and hence to meet requisite longevity targets under the harsh conditions and environments to and in which the gaskets are subjected.
In relatively recent times, prices of cork materials have increased significantly. In addition, the automotive industry has developed a perception that superior sealing results are achieved via uses of silicone rubbers. Moreover, materials that can be applied by silk screening techniques are associated with processes that are considerably less labor-intensive than the bonding and gluing processes associated with applications involving cork materials.
A gasket with improved sealing capability is needed particularly for automotive oil pan and valve cover applications; one employing improved sealing materials, and one involving less labor-intensive manufacturing processes.
The present invention offers an improved gasket for automotive non-combustion applications including valve cover and oil pan, as well as engine water coolant gaskets. A novel method of manufacturing the improved gasket is also disclosed. The gasket includes a perforated central planar core of metal sandwiched between two layers of a silicone foam rubber adapted to replace traditional cork gasket structures used for the same purpose. The gasket includes tangs or protrusions that extend from planar sides of the metallic core. As disclosed, the silicone rubber layers are applied as a silk-screened coating to both sides of the core, and the coating material employed includes a foaming agent that causes the material to expand during a subsequent oven-curing period.
The amount of heat-induced expansion of the silicone rubber layers is at least three times the original thickness of the as-applied coating. As disclosed, the oven cure takes place for approximately 10 minutes at 300 degrees Fahrenheit. The protrusions prevent the silicone rubber layers from being fully compressed during subsequent actual use of the gasket. The core is thus designed not to flatten out under normal gasket compression loads, as the peaks (i.e., extremities) of the protrusions act as compression loads stops to limit amount of permissible compression of the silicone rubber layers. The silicone rubber layers offer enhanced sealing effectiveness over traditional cork material facings.